Plane Geometry Under The Condition Of Hydrodynamics Stability Analysis

The hydrodynamic instability has been a focus of research in Inertial Confinement Fusion (ICF). It can destroy the symmetry and integrity of the capsule, and even fail the ignition. Inertial confinement fusion capsule implosions are inherently unstable. In particular, the Rayleigh-Taylor instability (RTI) tends at first to destroy the imploding shell and later hinders the formation of the central hot spot. The understanding of the growth of perturbations is of extreme important for achieving the ignition and high gain. It should be clear that the goal of central hot spot ignition depends most critically on how to control the instability. This paper makes use of two methods to measure the perturbation growth of sine modulated surface target and explore the system modulation transfer function (MTF).This paper makes use of face-on photography technology to investigate the Rayleigh-Taylor instability of sine modulated surface target and gain a vivid space and time resolved image. The experimental result are analyzed by using two method: 1.Figure out fundamental mode Fourier coefficient; 2. Figure out the D-value of wave crest and wave hollow, the two methods obtain the same perturbation growth factor. Moreover, the possible reasons for the little growth have been discussed and give the qualitative interpretation.Side-on radiography technology can directly demonstrate the change of perturbation amplitude on target surface. In the experiment at Shenguang II laser facility, this technology is used to detect rear surface perturbation caused by the ablation surface perturbation. The perturbation amplitude observed in the experiment is higher than expected. According to our analysis, two-dimensional effect is the main reason for larger perturbation growth of the rear surface. Because the target is set on the diagnosis hole of the holhraum, X-ray irradiate the part of the target corresponding to diagnostic hole. The rear surface perturbation, which is caused by the ablation surface perturbation, exists in the center and gradually spreads around. Based on above discussion, an optimized target design is presented at last, which suggests the target size along the direction of backlighting transmit should decrease. X-ray intensity distribution will have a change when it passes through the optical system in the hydrodynamic instability experiments, in order to get the perturbation change information,the system modulation transfer function should be investigated This chapter makes use of the knife-edge image to get the brim spread function, then the system modulation transfer function can be derived from the brim spread function. When the system modulation transfer function is known, the practical X-ray intensity distribution can be obtained through image intensity. Moreover, the product of subsystem modulation transfer function is the system modulation transfer function, this paper employs Fresnel-Kirchhoff's law of diffraction and Rayleigh -Sommerfeld's law of diffraction to simulates pinhole camera's point spread function (PSF), then gains this pinhole camera's modulation transfer function through Fourier analysis.